Doped insulator cap to reduce source/drain diffusion for germanium nmos transistors

ABSTRACT

Integrated circuit transistor structures are disclosed that reduce n-type dopant diffusion, such as phosphorous or arsenic, from the source region and the drain region of a germanium n-MOS device into adjacent insulator regions during fabrication. The n-MOS transistor device may include at least 75% germanium by atomic percentage. In an example embodiment, a dopant-rich insulator cap is deposited adjacent to the source and/or drain regions, to provide dopant diffusion reduction. In some embodiments, the dopant-rich insulator cap is doped with an n-type impurity including Phosphorous in a concentration between 1 and 10% by atomic percentage. In some embodiments, the dopant-rich insulator cap may have a thickness in the range of 10 to 100 nanometers and a height in the range of 10 to 200 nanometers.

BACKGROUND

Semiconductor devices are electronic components that exploit theelectronic properties of semiconductor materials, such as silicon (Si),germanium (Ge), and silicon germanium (SiGe). A field-effect transistor(FET) is a semiconductor device that includes three terminals: a gate, asource, and a drain. A FET uses an electric field applied by the gate tocontrol the electrical conductivity of a channel through which chargecarriers (e.g., electrons or holes) flow from the source to the drain.In instances where the charge carriers are electrons, the FET isreferred to as an n-channel device, and in instances where the chargecarriers are holes, the FET is referred to as a p-channel device.Standard dopant used for Si, Ge, and SiGe includes boron (B) for p-type(acceptor) dopant and phosphorous (P) or arsenic (As) for n-type (donor)dopant. Some FETs have a fourth terminal called the body or substrate,which can be used to bias the transistor. In addition,metal-oxide-semiconductor FETs (MOSFETs) include a gate dielectricbetween the gate and the channel. MOSFETs may also be known asmetal-insulator-semiconductor FETs (MISFETSs) or insulated-gate FETs(IGFETs). Complementary MOS (CMOS) structures use a combination ofp-channel MOSFET (p-MOS) and n-channel MOSFET (n-MOS) to implement logicgates and other digital circuits.

A FinFET is a MOSFET transistor built around a thin strip ofsemiconductor material (generally referred to as a fin). The conductivechannel of the FinFET device resides on the outer portions of the finadjacent to the gate dielectric. Specifically, current runs along/withinboth sidewalls of the fin (sides perpendicular to the substrate surface)as well as along the top of the fin (side parallel to the substratesurface). Because the conductive channel of such configurationsessentially resides along the three different outer, planar regions ofthe fin, such a FinFET design is sometimes referred to as a tri-gatetransistor. Other types of FinFET configurations are also available,such as so-called double-gate FinFETs, in which the conductive channelprincipally resides only along the two sidewalls of the fin (and notalong the top of the fin).

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the claimed subject matterwill become apparent as the following Detailed Description proceeds, andupon reference to the Drawings, wherein like numerals depict like parts.

FIGS. 1A-1B illustrate a method of forming an integrated circuit (IC)including at least one germanium (Ge)-rich n-MOS transistor employingone or more dopant-rich insulator caps, specifically, to help preventsource/drain (S/D) dopant from diffusing into adjacent insulatorregions, in accordance with some embodiments of the present disclosure.

FIGS. 2A-2Q illustrate example IC structures that are formed whencarrying out the method of FIGS. 1A-1B, in accordance with someembodiments

FIG. 3A illustrates an example cross-sectional view along the plane A-Ain FIG. 2P, in accordance with some embodiments.

FIG. 3B illustrates an example cross-sectional view along the plane B-Bin FIG. 2P, in accordance with some embodiments.

FIG. 4 illustrates a computing system implemented with integratedcircuit structures and/or transistor devices formed using the techniquesdisclosed herein, in accordance with some embodiments of the presentdisclosure.

These and other features of the present embodiments will be understoodbetter by reading the following detailed description, taken togetherwith the figures herein described. In the drawings, each identical ornearly identical component that is illustrated in various figures may berepresented by a like numeral. For purposes of clarity, not everycomponent may be labeled in every drawing. Furthermore, as will beappreciated, the figures are not necessarily drawn to scale or intendedto limit the described embodiments to the specific configurations shown.For instance, while some figures generally indicate straight lines,right angles, and smooth surfaces, an actual implementation of thedisclosed techniques may have less than perfect straight lines and rightangles, and some features may have surface topography or otherwise benon-smooth, given real-world limitations of fabrication processes.Further still, some of the features in the drawings may include apatterned and/or shaded fill, which is merely provided to assist invisually differentiating the different features. In short, the figuresare provided merely to show example structures

Although the following Detailed Description will proceed with referencebeing made to illustrative embodiments, many alternatives,modifications, and variations thereof will be apparent in light of thisdisclosure.

DETAILED DESCRIPTION

Integrated circuit transistor structures are disclosed that reducen-type dopant diffusion, such as phosphorous or arsenic, from the sourceand drain regions into adjacent insulator regions during fabrication ofn-MOS devices having a germanium-rich channel (e.g., germaniumconcentration of 75 atomic % or more, up to 100 atomic %). In an exampleembodiment, the structure includes an intervening diffusion glass cap,or structure, deposited between the n-MOS transistor and insulatorregions adjacent to the source and drain (S/D) regions. The diffusionglass cap is an insulator, such as silicon dioxide, which is doped withan n-type impurity to effectively provide dopant diffusion reductionfrom the S/D regions. In some embodiments, the n-type impurity isPhosphorous (P), which is implanted in the silicon dioxide to create thediffusion glass cap after forming the gate structure, such that the gatestructure prevents dopant implantation in regions of the insulator capadjacent to the channel region under the gate structure. In someembodiments, the concentration of n-type impurity implanted in theinsulator cap is in the range of 1 to 10 atomic %. In some embodiments,the dopant-rich insulator cap may have a thickness in the range of 10 to100 nanometers and a height in the range of 10 to 200 nanometers, aswill be explained in greater detail below. Numerous configurations andprocess flows will be apparent in light of this disclosure.

General Overview

The fabrication of Ge-rich n-MOS transistors is generally not practicaldue to the difficulty of maintaining a relatively high level of n-typedopant in the source/drain regions of the transistor. This is largelydue to the physical properties of Ge, wherein typical n-type dopants,such as phosphorous and arsenic, readily diffuse from the Ge-richsource/drain regions under the high temperature conditions associatedwith semiconductor fabrication processes. For instance, Ge-rich n-MOSdevices are susceptible to spilling of the n-type dopant from the S/Dregions into the surrounding insulator regions that separate andinsulate adjacent transistors. This spilling is particularly problematicunder the high temperature conditions associated with the semiconductorfabrication process. The resulting transistor device can exhibit poorS/D contact resistance due to the high energy barrier at themetal-semiconductor interface, which cannot be overcome by tunneling dueto the low dopant levels resulting from dopant diffusion out of the Gematerial. Such high S/D contact resistance can cause significantperformance degradation. These issues, resulting from dopant diffusion,are further exacerbated as transistor devices are scaled down to includesmaller critical dimensions, for example using sub-30 nm technology, andbeyond.

Thus, and in accordance with numerous embodiments of the presentdisclosure, techniques are provided for forming Ge-rich n-MOStransistors including one or more dopant-rich insulator caps, or cappingstructures, configured to separate source/drain fin structures fromadjacent insulator regions, as will be described in greater detailbelow. As can be understood based on this disclosure, the dopant-richinsulator caps proximate the source/drain regions help to inhibit theundesired diffusion of dopant (e.g., P, or As) from the S/D regions intoadjacent insulator regions. The dopant n-type impurity of thedopant-rich insulator cap, for example P, provides improved diffusionresistance properties as it reduces the dopant gradient between the S/Dregions and the adjacent insulator regions. In general, the dopant-richinsulator cap can effectively act as a dopant reflector whereinapproximately the same quantities of dopant diffuse in oppositedirections (e.g., from S/D region to insulator cap, and from insulatorcap back to S/D region), due to the relatively high concentration ofdopant impurity in the insulator cap. For example, in some embodiments,the insulator cap may have 2 to 10 times the dopant concentration of theS/D regions.

In some embodiments, the dopant-rich insulator cap may include silicondioxide (SiO₂) with phosphorous concentrations between 1 to 10 atomic %,although other compositions are possible. In some embodiments, thedopant-rich insulator cap may extend vertically upward (e.g., in theY-axis direction) in a range of 10 to 200 nanometers from the topsurface of an adjacent shallow trench isolation (STI) region. In someembodiments, the dopant-rich insulator cap may also extend horizontally(e.g., in the X-axis direction) in a range of 10 to 100 nanometers aboutthe source/drain fin structures.

Note that, as used herein, “Ge-rich” includes a Ge-containing body thatincludes over 50% Ge by atomic percentage, where the Ge orSi_(1-x)Ge_(x) (x>0.5) may be doped with any suitable material(s) and/oralloyed with other group IV elements (e.g., carbon and/or tin up to 2%by atomic percentage). For instance, in some embodiments, the Ge-richmaterial may be n-type doped, such as Ge:As, Ge:P, SiGe:P (with over 50%Ge by atomic percentage), or SiGe:As (with over 50% Ge by atomicpercentage), to provide some examples. Further, in some embodiments, theGe-rich material may include alloying of carbon and/or tin, such asGe:C, GeSn, SiGe:C, SiGeSn, GeSn:C, SiGeSn:C. Also note, that in someembodiments, Ge-rich may include a different threshold concentration (byatomic percentage) of Ge, such as at least 55, 60, 65, 70, 75, 80, 85,90, or 95%, for example. For instance, in some applications, embodimentswhere a Ge-rich channel region of a transistor includes at least 80% Geby atomic percentage may be desired, or even a pure Ge channel, such asto achieve a desired charge carrier mobility, for example. Further notethat the inclusion of Ge-rich material in a given feature as describedherein does not preclude the inclusion of materials other than Ge. Forinstance, in some embodiments, a Ge-rich channel region may include amultilayer structure that includes at least one Ge-rich layer and atleast one non-Ge-rich layer. However, in other embodiments, a Ge-richfeature has Ge-rich material be throughout essentially the entirety ofthat feature. Moreover, a Ge-rich channel region may include grading ofthe concentration of Ge throughout at least a portion of the channelregion, such that there may be one or more portions of that channelregion that include less than 50% Ge concentration by atomic percentage,and may even include no Ge content at all.

Also, as used herein, “group IV semiconductor material” (or “group IVmaterial” or generally, “IV”) includes at least one group IV element(e.g., silicon, germanium, carbon, tin), such as silicon (Si), germanium(Ge), silicon germanium (SiGe), and so forth. Note that alloys of groupIV elements are not to be confused with compounds of those elements.Therefore, when carbon is alloyed with any of the other group IVelements, the resulting alloy will be expressed herein as “X:C”, where“X” is the group IV element or alloy and “:C” indicates alloying withcarbon. For instance, silicon alloyed with carbon may be referred toherein as Si:C (thereby preventing confusion with silicon carbide(SiC)), silicon germanium alloyed with carbon may be referred to hereinas SiGe:C, germanium alloyed with carbon may be referred to herein asGe:C (thereby preventing confusion with germanium carbide (GeC)), and soforth. Also note that the molecular ratio or the atomic percentage ofthe elements included in a group IV alloy can be adjusted as desired.Further note that the use of “X:Z” herein indicates a dopingrelationship where “X” is an element or alloy doped by “Z”, such asarsenic-doped silicon germanium being represented by SiGe:As, orphosphorous-doped silicon germanium alloyed with carbon beingrepresented by SiGe:C:P, to provide some examples. Generally, whenreferring to group IV semiconductor material as described herein (e.g.,Si, SiGe, Ge, SiSn, SiGeSn, GeSn, Si:C, SiGe:C, Ge:C, SiSn:C, SiGeSn:C,GeSn:C), that group IV semiconductor material has a monocrystalline (orsingle-crystal) structure, unless otherwise stated, such as, forexample, where polycrystalline silicon (or poly-Si) may be utilized, asstated herein.

In some embodiments, the techniques can be used to benefit a multitudeof transistor devices. For instance, in some embodiments, the techniquesmay be used to benefit one or more n-channel transistor devices (wherethe charge carriers are electrons) such as n-channel MOSFET (n-MOS)devices. In some embodiments, the techniques described herein can beused to benefit complementary transistor circuits, such as CMOScircuits, where the techniques can be used to benefit one or more of theincluded n-channel transistors (e.g., n-MOS devices) making up a givenCMOS circuit. Further still, in some embodiments, the techniquesdescribed herein can be used to benefit transistors including amultitude of transistor configurations, such as planar and non-planarconfigurations, where the non-planar configurations may include finnedor FinFET configurations (e.g., dual-gate or tri-gate), gate-all-around(GAA) configurations (e.g., nanowire or nanoribbon), or some combinationthereof, to provide a few examples. Other example transistor devicesthat can benefit from the techniques described herein include few tosingle electron quantum transistor devices, for example.

As will be further appreciated, the Ge-rich n-MOS transistors, includingone or more dopant-rich insulator caps, or capping structures,configured to separate source/drain fin structures from adjacentinsulator regions, provided herein may also be intermixed on the samesubstrate with other transistor devices having channel regions devoid ofany germanium, such as transistors having silicon channel regions,gallium arsenide channel regions, indium arsenide channel regions,gallium indium arsenide channel regions, or some combination ofcompositionally diverse channel regions. Further note that some channelregions may be native to the substrate (i.e., fins formed from thesubstrate), while other channel regions may be epitaxially provided onthe substrate.

Note that, as used herein, the expression “X includes at least one of Aand B” refers to an X that may include, for example, just A only, just Bonly, or both A and B. To this end, an X that includes at least one of Aand B is not to be understood as an X that requires each of A and B,unless expressly so stated. For instance, the expression “X includes Aand B” refers to an X that expressly includes both A and B. Moreover,this is true for any number of items greater than two, where “at leastone of” those items is included in X. For example, as used herein, theexpression “X includes at least one of A, B, and C” refers to an X thatmay include just A only, just B only, just C only, only A and B (and notC), only A and C (and not B), only B and C (and not A), or each of A, B,and C. This is true even if any of A, B, or C happens to includemultiple types or variations. To this end, an X that includes at leastone of A, B, and C is not to be understood as an X that requires each ofA, B, and C, unless expressly so stated. For instance, the expression “Xincludes A, B, and C” refers to an X that expressly includes each of A,B, and C. Likewise, the expression “X included in at least one of A andB refers to an X that may be included, for example, in just A only, injust B only, or in both A and B. The above discussion with respect to “Xincludes at least one of A and B” equally applies here, as will beappreciated.

Use of the techniques and structures provided herein may be detectableusing tools such as: electron microscopy including scanning/transmissionelectron microscopy (SEM/TEM), scanning transmission electron microscopy(STEM), nano-beam electron diffraction (NBD or NBED), and reflectionelectron microscopy (REM); composition mapping; x-ray crystallography ordiffraction (XRD); energy-dispersive x-ray spectroscopy (EDS); secondaryion mass spectrometry (SIMS); time-of-flight SIMS (ToF-SIMS); atom probeimaging or tomography; local electrode atom probe (LEAP) techniques; 3Dtomography; or high resolution physical or chemical analysis, to name afew suitable example analytical tools. In particular, in someembodiments, such tools may indicate an integrated circuit (IC)including at least one Ge-rich n-MOS transistor that includes adopant-rich insulator cap, or capping structure, doped with n-typeimpurities, as described herein. For instance, in some such embodiments,the techniques may be detected by observing (e.g., via SEM/TEM) that Pis present in a dopant-rich insulator cap adjacent to one or more S/Dregions. In some embodiments, the techniques and structures describedherein may be detected based on the benefits derived therefrom, such asby observing a Ge-rich n-MOS source/drain fin structure that does notexhibit reduced levels of dopant (e.g., P or As) resulting fromdiffusion into adjacent insulator regions, as a result of thedopant-rich insulator cap as described herein (e.g., as compared toGe-rich n-MOS transistors that do not employ the techniques describedherein). Thus, in some embodiments, the techniques described herein mayenable forming enhanced performance Ge-rich transistor devices withsub-30 nm technology and beyond, which can also be detected andmeasured. Numerous configurations and variations will be apparent inlight of this disclosure.

Methodology and Architecture

FIG. 1 (1A and 1B) illustrate method 100 of forming an integratedcircuit (IC) including at least one Ge-rich n-MOS transistor employingone or more dopant-rich insulator caps doped with an n-type impurity,specifically, to help prevent or otherwise inhibit S/D dopant fromdiffusing into the adjacent insulator regions, in accordance with someembodiments of the present disclosure. FIGS. 2A-Q illustrate example ICstructures that are formed when carrying out method 100 of FIG. 1, inaccordance with some embodiments. The structures of FIGS. 2A-Q areprimarily depicted and described herein in the context of forming finnedor FinFET transistor configurations (e.g., tri-gate transistorconfigurations), for ease of illustration. However, in some embodiments,the techniques can be used to form transistors of any suitable geometryor configuration, as can be understood based on this disclosure. Alsonote that the techniques and structures are primarily depicted anddescribed in the context of forming metal-oxide-semiconductorfield-effect transistors (MOSFETs). However, the present disclosure isnot intended to be so limited unless stated otherwise. Further note thatmethod 100 includes a primary path that illustrates a gate lasttransistor fabrication process flow that can be employed in accordancewith some embodiments. However, in other embodiments, a gate firstprocess flow may be employed instead, as will be described herein (andwhich is illustrated with the alternative gate first flow 100′ indicatorin FIG. 1). Numerous variations and configurations will be apparent inlight of this disclosure.

Method 100 of FIG. 1 (referring now to FIG. 1A) includes patterning 102hardmask on a substrate, such as patterning hardmask 210 a on substrate200 of FIG. 2A to form the example structure 210 b of FIG. 2B, inaccordance with some embodiments. In some embodiments, hardmask 210 amay be deposited or otherwise formed on substrate 200 using any suitabletechniques as will be apparent in light of this disclosure. For example,hardmask 210 a may be blanket deposited or otherwise grown on substrate200 using chemical vapor deposition (CVD), atomic layer deposition(ALD), physical vapor deposition (PVD), spin-on processing, and/or anyother suitable process to form hardmask 210 a on substrate 200. In someinstances, the top surface of substrate 200 on which hardmask 210 a isto be deposited may be treated (e.g., via chemical treatment, thermaltreatment, etc.) prior to deposition of the hardmask 210 a material.After being blanket formed on substrate 200, hardmask 210 a may then bepatterned using any suitable techniques, such as one or more lithographyand etch processes, for example, to produce structure 210 b. Hardmask210 a may include any suitable material, such as oxide material, nitridematerial, and/or any other suitable masking material, for example.Specific oxide and nitride materials may include silicon oxide, titaniumoxide, hafnium oxide, aluminum oxide, silicon nitride, and titaniumnitride, just to name a few examples. In some cases, the material ofhardmask 210 a may be selected based on the material of substrate 200,for example.

Substrate 200, in some embodiments, may be: a bulk substrate includinggroup IV semiconductor material (e.g., Si, Ge, SiGe), group III-Vsemiconductor material (e.g., GaAs, GaAsSb, GaAsIn), and/or any othersuitable material(s) as will be apparent in light of this disclosure; anX on insulator (XOI) structure where X is one of the aforementionedmaterials (e.g., group IV and/or group III-V semiconductor material) andthe insulator material is an oxide material or dielectric material orsome other electrically insulating material, such that the XOI structureincludes the electrically insulating material layer between twosemiconductor layers; or some other suitable multilayer structure wherethe top layer includes one of the aforementioned semiconductor materials(e.g., group IV and/or group III-V semiconductor material). The use of“group IV semiconductor material” (or “group IV material” or generally,“IV”) herein includes at least one group IV element (e.g., silicon,germanium, carbon, tin), such as silicon (Si), germanium (Ge), silicongermanium (SiGe), and so forth. The use of “group III-V semiconductormaterial” (or “group III-V material” or generally, “III-V”) hereinincludes at least one group III element (e.g., aluminum, gallium,indium) and at least one group V element (e.g., nitrogen, phosphorus,arsenic, antimony, bismuth), such as gallium arsenide (GaAs), indiumgallium arsenide (InGaAs), indium aluminum arsenide (InAlAs), galliumphosphide (GaP), gallium antimonide (GaSb), indium phosphide (InP), andso forth. Note that group III may also be known as the boron group orIUPAC group 13, group IV may also be known as the carbon group or IUPACgroup 14, and group V may also be known as the nitrogen family or IUPACgroup 15, for example. In some embodiments, substrate 200 may includeGe-rich material to be used in the channel region of one or moretransistors.

In some embodiments, substrate 200 may be doped with any suitable n-typeand/or p-type dopant. For instance, in the case, of a Si substrate, theSi may be p-type doped using a suitable acceptor (e.g., boron) or n-typedoped using a suitable donor (e.g., phosphorous, arsenic), to providesome example cases. However, in some embodiments, substrate 200 may beundoped/intrinsic or relatively minimally doped (such as including adopant concentration of less than 1E16 atoms per cubic cm), for example.In some embodiments, substrate 200 may include a surface crystallineorientation described by a Miller index of (100), (110), or (111), orits equivalents, as will be apparent in light of this disclosure.Although substrate 200, in this example embodiment, is shown as having athickness (dimension in the Y-axis direction) similar to other layersshown in subsequent structures for ease of illustration, in someinstances, substrate 200 may be much thicker than the other layers, suchas having a thickness in the range of 50 to 950 microns, for example, orany other suitable thickness as will be apparent in light of thisdisclosure. In some embodiments, substrate 200 may be used for one ormore other IC devices, such as various diodes (e.g., light-emittingdiodes (LEDs) or laser diodes), various transistors (e.g., MOSFETs orTFETs), various capacitors (e.g., MOSCAPs), variousmicroelectromechanical systems (MEMS), various nanoelectromechanicalsystems (NEMS), various radio frequency (RF) devices, various sensors,or any other suitable semiconductor or IC devices, depending on the enduse or target application. Accordingly, in some embodiments, thestructures described herein may be included in a system-on-chip (SoC)application, as will be apparent in light of this disclosure.

Method 100 of FIG. 1 continues with performing 104 a shallow trenchrecess (STR) etch to form fins 202 from substrate 200, thereby formingthe resulting example structure shown in FIG. 2C, in accordance withsome embodiments. In some embodiments, the STR etch 104 used to formtrenches 215 and fins 202 may include any suitable techniques, such asvarious masking processes and wet and/or dry etching processes, forexample. In some cases, STR etch 104 may be performed in-situ/withoutair break, while in other cases, STR etch 104 may be performed ex-situ,for example. Trenches 215 may be formed with varying widths (dimensionin the X-axis direction) and depths (dimension in the Y-axis direction)as can be understood based on this disclosure. For example, multiplehardmask patterning 102 and STR etching 104 processes may be performedto achieve varying depths in the trenches 215 between fins 202. Fins 202may be formed to have varying widths Fw (dimension in the X-axisdirection) and heights Fh (dimension in the Y-axis direction). Note thatalthough hardmask structures 210 b are still present in the examplestructure of FIG. 2C, in some cases, that need not be the case, as theymay have been consumed during the STR etch, for example. Further notethat, while the fins 202 are shown as relatively rectangular in nature(with straight sides and a flat top) for ease of depiction, in reality,the fins may include a tapered profile where the top of the fin isnarrower than the base of the fin (as viewed in a cross-section takenperpendicular to the fin). Moreover, the very top of the fin may berounded, rather than flat. Numerous other real-world geometries will beappreciated.

In some embodiments, the fin widths Fw (dimension in the horizontal orX-axis direction) may be in the range of 2-400 nm (or in a subrange of2-10, 2-20, 2-50, 2-100, 2-200, 4-10, 4-20, 4-50, 4-100, 4-200, 4-400,5-20, 10-20, 10-50, 10-100, 10-200, 10-400, 50-100, 50-200, 50-400,100-400 nm, or any other sub-range), for example, or any other suitablevalue or range as will be apparent in light of this disclosure. In someembodiments, the fin heights Fh (dimension in the vertical or Y-axisdirection) may be in the range of 4-800 nm (or in a subrange of 4-10,4-20, 4-50, 4-100, 4-200, 4-400, 10-20, 10-50, 10-80, 10-100, 10-200,10-400, 10-800, 50-100, 50-200, 50-400, 50-800, 100-400, 100-800,400-800 nm, or any other sub-range), for example, or any other suitablevalue or range as will be apparent in light of this disclosure. In someembodiments, the fin heights Fh may be at least 10, 25, 35, 50, 75, 100,125, 150, 175, 200, 300, 400, 500, 600, 700, or 800 nm tall, or anyother desired height as will be apparent in light of this disclosure. Insome embodiments, the height to width ratio of the fins (Fh:Fw) may begreater than 1, such as greater than 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6,7, 8, 9, or 10, or greater than any other suitable threshold ratio, aswill be apparent in light of this disclosure. Note that the trenches 215and fins 202 are each shown as having essentially the same sizes andshapes in this example structure for ease of illustration; however, thepresent disclosure is not intended to be so limited. For example, insome embodiments, the fins 202 may be formed to have varying heights Fh,varying widths Fw, varying starting points (or varying startingheights), varying shapes, and/or any other suitable variations as willbe apparent in light of this disclosure. Moreover, trenches 215 may beformed to have varying depths, varying widths, varying starting points(or varying starting depths), varying shapes, and/or any other suitablevariations as will be apparent in light of this disclosure. Further notethat although four fins 202 are shown in the example structure of FIG.2C for ease of illustration, any number of fins may be formed, such asone, two, three, five, ten, hundreds, thousands, millions, and so forth,as can be understood based on this disclosure. FIG. 2D illustrates across-sectional (2-dimensional) view of the example structure shown inFIG. 2C for reference.

Method 100 of FIG. 1 continues with depositing 106 shallow trenchisolation (STI) material 220 to form the example resulting structure ofFIG. 2E, in accordance with some embodiments. Deposition 106 of STImaterial 220 may include any suitable deposition techniques, such asthose described herein (e.g., CVD, ALD, PVD), or any other suitabledeposition process. In some embodiments, STI material 220 (which may bereferred to as an STI layer or STI structure) may include any suitableelectrically insulating material, such as one or more dielectric, oxide(e.g., silicon dioxide), and/or nitride (e.g., silicon nitride)materials. In some embodiments, the material of STI layer 220 may beselected based on the material of substrate 200. For instance, in thecase of a Si substrate, the STI material may be selected to be silicondioxide or silicon nitride, to provide some examples. Method 100 of FIG.1 further continues with planarizing/polishing 108 the structure to formthe example resulting structure of FIG. 2F, in accordance with someembodiments. The planarizing and/or polishing process(es) performedafter forming STI material 220 may include any suitable techniques, suchas chemical-mechanical planarization/polishing (CMP) processes, forexample. Note that the hardmask 210 b is removed by this planarization,in this example embodiment. In other embodiments, the hardmask 210 b mayremain.

Method 100 of FIG. 1 continues with recessing 110 the native finmaterial 202. In embodiments where the fins 202 are to be removed andreplaced with replacement semiconductor material (e.g., to be used inthe channel region of one or more transistor devices), the structure ofFIG. 2F enables such processing. For example, continuing from thestructure of FIG. 2F to the structure of FIG. 2G, fins 202 may berecessed or removed using selective etch processing (e.g., for a givenetchant, the semiconductor material of fins 202 is removed selective tothe insulator material of STI layer 220) to form fin-shaped trenches 209between STI material 220 in which replacement semiconductor material canbe deposited/grown (e.g., using any suitable techniques, such as CVD,metal-organic CVD (MOCVD), ALD, molecular beam epitaxy (MBE), PVD). Thedepth of the etch can vary from one embodiment to the next. In theembodiment shown, a portion of the native fin is left so as to provide apedestal or fin stub 207 on which the replacement fin material can bedeposited. In other embodiments, the native fin can be completelyremoved, so as to be flush with the top surface of substrate 200 toprovide no pedestal or fin stub, or even below the top surface ofsubstrate 200 so as to provide an inverted pedestal or fin stub.

Method 100 of FIG. 1 continues with deposition 112 of replacementsemiconductor fin material. For instance, FIG. 2H illustrates recess andreplace processing to form a replacement material fin 230, in accordancewith some embodiments. Replacement fin 230 (and generally, anyreplacement fin formed) may include any suitable semiconductor material(e.g., group IV and/or III-V semiconductor material). For instance,replacement fins including SiGe or Ge may be formed by removing nativeSi fins during such processing and replacing them with the SiGe or Gematerial, to provide some examples. In addition, replacement fin 230 mayinclude any suitable n-type or p-type dopant, or be undoped orlightly-doped. In some embodiments, replacement material fins, such asreplacement fin 230 of FIG. 2H may be formed using alternativeprocessing. For instance, in some embodiments, replacement material finsmay be formed by blanket-growing the replacement material on thesubstrate (e.g., using epitaxial deposition processing) and thenpatterning the replacement material into replacement material fins, toprovide an example alternative. Note that replacement fin 230 isillustrated with patterning/shading to merely assist with visuallyidentifying that feature. In any such cases, the resulting structure canbe planarized to provide a relatively flat top surface, as generallyshown in FIG. 2H.

Method 100 of FIG. 1 continues with recessing 114 of the STI material220 between fins, as shown in FIG. 2I, to cause at least a portion 231of fins 230 to exude from the STI plane, thereby forming the resultingexample structure shown in FIG. 2I, in accordance with some embodiments.Recessing 114 may be performed using any suitable techniques, such asusing one or more wet and/or dry etch processes that allow the STImaterial 220 to be selectively recessed relative to the material of fin230, and/or any other suitable processing as will be apparent in lightof this disclosure. As can be understood based on this disclosure,exposed portions 231 of fins 230 may be used to provide the channelregion of one or more transistors, such that fin portions 231 (theportions of fins 230 above the top plane of STI layer 220 after recess114 has been performed) may be referred to as channel portions herein,for example. More specifically, the fin portion 231 under the gatestructure to be subsequently formed is generally referred to as thechannel portion, with the source and drain regions to be formed toeither side of the channel portion, such that the channel is between thesource and drain regions. Moreover, the portions of fins 230 below thetop plane of STI layer 220 are indicated as portions 232, where suchportions may be referred to as sub-channel portions, for example.

As shown in FIG. 2I, the portions 231 of fins 230 exuding above the topplane of STI layer 220 have a fin height indicated as Fh, which may bein the range of 4-800 nm (e.g., in the subrange of 4-10, 4-20, 4-50,4-100, 4-200, 4-400, 10-20, 10-50, 10-80, 10-100, 10-200, 10-400,10-800, 50-100, 50-200, 50-400, 50-800, 100-400, 100-800, 400-800 nm, orsome other sub-range), for example, or any other suitable value orrange, as will be apparent in light of this disclosure. In some specificembodiments, the fin heights Fh may be at least 10, 25, 35, 50, 75, 100,125, 150, 175, 200, 300, 400, 500, 600, 700, or 800 nm tall. Also notethat in embodiments employing planar transistor configurations, recessprocess 114 need not be performed, as the transistor may be formed usingthe top surface of semiconductor body 230 as shown in FIG. 2H, forexample.

Note that all of the fins are shown as being replaced in the exampleembodiment of FIG. 2I; however, the present disclosure is not intendedto be so limited. In some embodiments, as illustrated in FIG. 2J, only asubset may be replaced (e.g., such that some replacement fins 230 areavailable for subsequent processing and some native fins 202 remain forsubsequent processing). FIG. 2J′ illustrates this in a perspective view.

Further, in some embodiments, the recess and replace process may beperformed as many times as desired to form as many subsets ofreplacement fins as desired by masking off the areas not to be processesfor each replacement fin subset processing. This is illustrated, forexample, in FIG. 2K where two different sets of replacement fins 230 and240 are shown. In some such embodiments, a first subset of replacementfins may be formed for n-channel transistors (e.g., where the firstreplacement material is selected to increase electron mobility) and asecond subset of replacement fins may be formed for p-channeltransistors (e.g., where the second replacement material is selected toincrease hole mobility). So, for instance, some of the native fins 202are removed and replaced with a first material 230 (e.g., Ge-richmaterial) and others of the native fins 202 are removed and replacedwith a second material 240 (e.g., III-V material). FIG. 2K′ illustratesthis in a perspective view.

Further still, in some embodiments, a multilayer replacement fin may beformed to enable the subsequent formation of nanowires or nanoribbons inthe channel region of one or more transistors, where some of the layersin the multilayer replacement fin are sacrificial and intended to beremoved via selective etching (e.g., during replacement gateprocessing). Numerous such fin replacement schemes can be used, as willbe apparent.

Method 100 of FIG. 1 (referring now to FIG. 1B) continues withoptionally forming 116 a dummy gate stack to form the example resultingstructure of FIG. 2L, in accordance with some embodiments. Recall thatmethod 100 is primarily described herein in the context of a gate lasttransistor fabrication process flow, where the processing includesforming a dummy gate stack, performing the S/D processing, and thenforming the final gate stack after the S/D regions have been processed.However, in other embodiments, the techniques may be performed using agate first process flow. In such an example case, process 116 (forming adummy gate stack) would not be performed, and thus, process 116 may beoptional in some embodiments (such as those employing the gate firstprocess flow). This is reflected with the alternative location forperforming 122 final gate stack processing, which is shown as theoptional gate first flow 100′ in FIG. 1, where performing 122 the finalgate stack processing would instead occur at the location of box 116 inembodiments employing a gate first process flow, for example. However,the description of method 100 will continue using a gate last processflow, to allow for such a flow (which generally includes additionalprocessing) to be adequately described.

Continuing with forming 116 a dummy gate stack, such a dummy gate stack(where employed) may include dummy gate dielectric 242 and dummy gateelectrode 244, thereby forming the example resulting structure of FIG.2L, in this example embodiment. In this example embodiment, dummy gatedielectric 242 (e.g., dummy oxide material) and dummy gate electrode 244(e.g., dummy poly-silicon material) may be used for a replacement gateprocess. Note that gate spacers 250, on either side of the dummy gatestack were also formed, and such gate spacers 250 can be used to helpdetermine the channel length and/or to help with replacement gateprocesses, for example. As can be understood based on this disclosure,the dummy gate stack (and gate spacers 250) can help define the channelregion and source/drain (S/D) regions of each transistor device, wherethe channel region is below the dummy gate stack (as it will be locatedbelow the final gate stack), and the S/D regions are on either side ofand adjacent to the channel region. Note that because the IC structuresare being described in the context of forming finned transistors, thefinal gate stack will also be adjacent to either side of the fin, as thegate stack will reside along the top and opposing sidewalls of thefinned channel regions, in embodiments employing a finned (e.g., FinFET)configuration.

Formation of the dummy gate stack may include depositing the dummy gatedielectric material 242 and dummy gate electrode material 244,patterning the dummy gate stack, depositing gate spacer material 250,and performing a spacer etch to form the structure shown in FIG. 2L, forexample. Gate spacers 250 may include any suitable material, such as anysuitable electrical insulator, dielectric, oxide (e.g., silicon oxide),and/or nitride (e.g., silicon nitride) material, as will be apparent inlight of this disclosure. Note that in some embodiments, as previouslydescribed, the techniques described herein need not include forming adummy gate stack, such that a final gate stack may be formed in thefirst instance. Regardless, the end structure will include a final gatestack, as will be apparent in light of this disclosure. Also note thatin some embodiments, a hardmask may be formed over the dummy gate stack(which may or may not also be formed over gate spacers 250) to protectthe dummy gate stack during subsequent processing, for example. Theprevious relevant description of hardmask 210 is equally applicable tosuch a hardmask feature, where employed.

Method 100 of FIG. 1 continues with performing 118 the source/drain(S/D) region processing to form the example resulting structure of FIG.2M, in accordance with some embodiments. The S/D region processing 118may include an etch and replace process, where portions of thereplacement fins 230 are removed in the S/D regions by way of aselective etch (or any other suitable etch scheme), yielding the examplestructure of FIG. 2M. It will be appreciated that, although FIG. 2Mshows the entire replacement material that occupies the source/drainregion as being removed, in some embodiments the process may remove onlya portion of the replacement material. In still other embodiments, theprocess may remove the entire replacement material in the source/drainas well as a portion of the native selection fin.

The process may continue with epitaxial deposition of the desired S/Dmaterial thereby forming the bulk S/D regions 261 (e.g., p-MOS) and 262(e.g., n-MOS), in this example embodiment. In some embodiments, S/Dregions 261, 262 can be formed using any suitable techniques, such asone or more of the deposition processes described herein (e.g., CVD,ALD, PVD, MBE), and/or any other suitable processes as will be apparentin light of this disclosure. In some such embodiments, S/D regions 261,262 may be formed using a selective deposition process, e.g., such thatthe material of the features only or significantly only grows (or onlygrows in a monocrystalline structure) from the exposed semiconductormaterial, as can be understood based on this disclosure. In otherembodiments, the S/D regions 261, 262 are implantation doped portions ofthe fins (202, 230, 240).

Note that the S/D regions 261, 262 are referred to herein as such forease of description, but each S/D region may be either a source regionor a drain region, such that the corresponding S/D region (on the otherside of the channel region, and thus, on the other side of the dummygate stack) is the other of the source region and drain region, therebyforming a source and drain region pair. For instance, as shown in FIG.2M, there are three channel regions and three corresponding S/D regionpairs 261, 262, 261.

In some embodiments, the S/D regions may include any suitablesemiconductor material as will be apparent in light of this disclosure,such as monocrystalline group IV semiconductor material. For instance, agiven S/D region may include at least one of Si, Ge, Sn, and C. In someembodiments, a given S/D region may or may not include n-type and/orp-type dopant (such as in one of the schemes described herein). Wherepresent, the dopant may be included in a concentration in the range of1E17 to 5E21 atoms per cubic cm or greater, for example. In someembodiments, a given S/D region may include grading (e.g., increasingand/or decreasing) of the concentration of one or more materials withinthe feature, such as the grading of a semiconductor material componentconcentration and/or the grading of the dopant concentration, forexample. For instance, in some such embodiments, the dopantconcentration included in a given S/D region may be graded such that itis lower near the corresponding channel region and higher near thecorresponding S/D contact, which may be achieved using any suitableprocessing, such as tuning the amount of dopant in the reactant flow(e.g., during an in-situ doping scheme), to provide an example. In someembodiments, a given S/D region may include a multilayer structure thatincludes at least two compositionally different material layers. Forinstance, in the case of a Fermi Field FET (FFFET) device, the sourceregion may include a multilayer structure that includes a p-type dopedregion and n-type doped region, in accordance with some embodiments. Insome embodiments, a given S/D region may be raised such that it extendshigher than a corresponding channel region (e.g., in the vertical orY-axis direction).

In some embodiments, S/D region 261, 262 may have different shapes andconfigurations, depending on the forming processes used, as will beapparent in light of this disclosure. For instance, in the examplestructure of FIG. 2M the S/D regions include three-dimensional diamondshapes, with two top surfaces that are faceted (e.g., with {111}faceting) as shown. Other example structures may be formed, inaccordance with some embodiments, including a rounded (or curved) andunfaceted top, and the rounded or curved S/D region may extend past theunderlying sub-fin portion in the X-axis direction. As can be understoodbased on this disclosure, S/D regions including any shape (such as thediamond shape of S/D region 261, 262, or a rounded shape) can benefitfrom the techniques described herein.

In some embodiments, one of the S/D regions in a corresponding S/Dregion pair (such as region 261 on one side of the dummy gate stack) maybe processed separately than the other S/D region in that pair (such asregion 261 on the opposite side of the dummy gate stack), such that acorresponding S/D pair may include different material, dopant type,dopant concentration, sizes, shapes, and/or any other suitabledifference as can be understood based on this disclosure. For instance,in the case of a TFET device, one of the S/D regions may include n-typedoped semiconductor material and the other of the S/D regions mayinclude p-type doped semiconductor material, to provide an example case,such that the n-type S/D region may be processed separately from thep-type S/D region. The separate processing may be achieved using anysuitable techniques, such as masking off S/D regions not to be processedto allow processing of other S/D regions, and then masking off the otherS/D regions to allow processing of the originally masked off S/Dregions, for example. In some embodiments, a given S/D region mayinclude the same or a similar material composition (e.g., within 1%different) as the corresponding/adjacent channel region (such as bothincluding the same Ge-rich material). However, in other embodiments, agiven S/D region may include a different material composition (e.g., atleast 1, 2, 3, 4, 5, or 10% different) relative to thecorresponding/adjacent channel region, for example.

Method 100 of FIG. 1 continues with depositing 120 the dopant-richinsulator cap layer or region 212 to form the example resultingstructure of FIG. 2N, in accordance with some embodiments.

Dopant-rich insulator cap layer 212 is configured to separatesource/drain fin structures 262 from adjacent undoped insulator regions,as will be described below. As can be understood based on thisdisclosure, the introduction of one or more dopant-rich insulator capshelps to inhibit the undesired diffusion of n-type dopant or impurities(e.g., P, or As) of the S/D regions into the adjacent insulator regions.In some embodiments, the dopant-rich insulator cap may include silicondioxide (SiO₂) with phosphorous concentrations between 1 to 10 atomic %,although other compositions are possible. In some embodiments, thedopant-rich insulator cap may extend vertically upward (e.g., in theY-axis direction) in a range of 10 to 200 nanometers from the topsurface of an adjacent shallow trench isolation (STI) region 220, asindicated by h in FIG. 2N. In some embodiments, the dopant-richinsulator cap may also extend horizontally (e.g., in the X-axisdirection) in a range of 10 to 100 nanometers about the source/drain finstructures, as indicated by w in FIG. 2N. Other suitable ranges arepossible and will be apparent in light of this disclosure.

In general, the dopant-rich insulator cap layer 212 can be any materialor composition that reduces or inhibits the depletion of S/D dopant thatwould otherwise be allowed to leave the S/D faster than it isreplenished. The insulator cap provides a benefit since dopant thatwould otherwise leave the S/D regions and move into the neighboringinsulator regions, particularly in the context of an n-type Ge-richchannel device, is no longer available to activate free electrons in theS/D and therefore contributes to degraded device performance. In someembodiments, the concentration of dopant, in the dopant-rich insulatorcap layer 212, adjacent to n-type Ge S/D will exceed 2E21 phosphorousand arsenic atoms per cubic cm. This concentration is distinguishablefrom unintentional n-type dopant diffusion from the Ge S/D to adjacentundoped insulators, in the absence of a dopant-rich insulator cap layer,where the concentration of phosphorous and arsenic atoms would be gradeddownward from a peak of about 7E20 atoms per cubic cm.

Deposition 120 of dopant-rich insulator cap layer 212 may include anysuitable deposition techniques, such as those described herein (e.g.,CVD, ALD, PVD), or any other suitable deposition process. In someembodiments, dopant-rich insulator cap layer material 212 may be blanketdeposited over all or most of the S/D regions (e.g., both p-MOS 261 andn-MOS 262), followed by a masking and etching process to remove thematerial from the p-MOS regions 261.

Method 100 of FIG. 1 continues with performing 122 the final gate stackprocessing to form the example resulting structure of FIG. 2P, inaccordance with some embodiments. As shown in FIG. 2P, the processing inthis example embodiment included depositing interlayer dielectric (ILD)layer 270 on the structure of FIG. 2N, followed by planarization and/orpolishing (e.g., CMP) to reveal the dummy gate stack. Note that ILDlayer 270 may include a multilayer structure, even though it isillustrated as a single layer. Further note that in some cases, ILDlayer 270 and STI material 220 may not include a distinct interface asshown in FIG. 2P, particularly where, e.g., the ILD layer 270 and STImaterial 220 include the same dielectric material (e.g., where bothinclude silicon dioxide). In general, the ILD layer 270 may include anydesired electrical insulator, dielectric, oxide (e.g., silicon oxide),and/or nitride (e.g., silicon nitride) material, as will be apparent inlight of this disclosure. In some embodiments, the ILD layer 270 may bereferred to as an undoped insulation layer.

The gate stack processing, in this example embodiment, continues withremoving the dummy gate stack (including dummy gate 244 and dummy gatedielectric 242) to allow for the final gate stack to be formed. Recallthat in some embodiments, the formation of the final gate stack, whichincludes gate dielectric 282 and gate electrode 284, may be performedusing a gate first flow. In such embodiments, the final gate stackprocessing may have been alternatively performed at box 116, instead offorming a dummy gate stack. However, in this example embodiment, thefinal gate stack is formed using a gate last flow (also called areplacement gate or replacement metal gate (RMG) process). Regardless ofwhether gate first or gate last processing is employed, the final gatestack can include gate dielectric 282 and gate electrode 284 as shown inFIG. 2M and described herein.

Note that when the dummy gate is removed, the channel region of fins 202(or replacement fins 230, 240), which is the portion of the fins thatwere covered by the dummy gate stack, are exposed to allow for anydesired processing of those channel regions. Such processing of a givenchannel region may include various different techniques, such asremoving and replacing the channel region with replacement material,doping the channel region as desired, forming the channel region intoone or more nanowires (or nanoribbons) for a gate-all-around (GAA)transistor configuration, cladding the channel region,cleaning/polishing the channel region, and/or any other suitableprocessing as will be apparent in light of this disclosure.

In some embodiments, a given channel region of a transistor device mayinclude monocrystalline Ge-rich group IV semiconductor material, such asmonocrystalline Ge or monocrystalline SiGe with over 50% Ge by atomicpercentage, and/or any other suitable material as will be apparent inlight of this disclosure. In general, a given channel region may includeat least one of silicon (Si) and germanium (Ge), to provide someexamples. In some embodiments, the channel region may be lightly doped(e.g., with any suitable n-type and/or p-type dopant) orintrinsic/undoped (or nominally undoped, with a dopant concentrationless than 1E16 atoms per cubic cm), depending on the particularconfiguration. In some embodiments, a given channel region may includegrading (e.g., increasing and/or decreasing) of the concentration of oneor more materials within the feature, such as the grading of asemiconductor material component concentration and/or the grading of thedopant concentration, for example. In some embodiments, a given channelregion may include a multilayer structure that includes at least twocompositionally different material layers. As can be understood based onthis disclosure, the channel region is at least below the gate stack, inthis example embodiment. For instance, in the case of a finnedtransistor configuration, the channel region may be below and betweenthe gate stack, as the stack is formed on a top and opposing sides of asemiconductor body or fin. However, if the transistor device wereinverted and bonded to what will be the end substrate, then the channelregion may be above the gate. Therefore, in general, the gate structureand channel region may include a proximate relationship, where the gatestructure is near the channel region such that it can exert control overthe channel region in an electrical manner, in accordance with someembodiments. Further, in the case of a nanowire (or nanoribbon or GAA)transistor configuration, the gate stack may completely surround eachnanowire/nanoribbon in the channel region (or at least substantiallysurround each nanowire, such as surrounding at least 70, 80, or 90% ofeach nanowire). Further still, in the case of a planar transistorconfiguration, the gate stack may simply be above the channel region.

Note that the S/D regions 261, 262 are adjacent to either side of acorresponding channel region, such as can be seen in FIG. 2P, forexample. Also note that the configuration/geometry of a transistorformed using the techniques described herein may primarily be describedbased on the shape of the respective channel region of that transistor.For instance, a nanowire (or nanoribbon or GAA) transistor may bereferred to as such because it includes one or more nanowires (ornanoribbons) in the channel region of that transistor and because thegate stack (including the gate) wraps around (or at least substantiallywraps around) each nanowire (or nanoribbon). However, the transistortype (e.g., MOSFET, TFET, FFFET, or other suitable type) may bedescribed based on the doping and/or operating scheme of the source,channel, and drain regions, and thus those respective regions may beused to determine the type or classification of a given transistor, forexample. For instance, MOSFET and TFET transistors may structurally bevery similar (or the same), but they include different doping schemes(e.g., source-drain doping schemes for MOSFET of p-p or n-n versus p-nor n-p for TFET).

Continuing with performing 122 final gate stack processing, after thedummy gate has been removed and any desired channel region processinghas been performed, the final gate stack can then be formed, inaccordance with some embodiments. In this example embodiment, the finalgate stack includes gate dielectric 282 and gate electrode 284, as shownin FIG. 2P. The gate dielectric 282 may include any suitable dielectric(such as silicon dioxide, and/or a high-k dielectric material), as willbe apparent in light of this disclosure. Examples of high-k dielectricmaterials include, for instance, hafnium oxide, hafnium silicon oxide,lanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconiumsilicon oxide, tantalum oxide, titanium oxide, barium strontium titaniumoxide, barium titanium oxide, strontium titanium oxide, yttrium oxide,aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate, toprovide some examples. In some embodiments, an annealing process may becarried out on the gate dielectric 282 to improve its quality whenhigh-k dielectric material is used. The gate electrode 284 may include awide range of materials, such as various suitable metals or metalalloys, such as aluminum (Al), tungsten (W), titanium (Ti), tantalum(Ta), copper (Cu), and carbides and nitrides thereof, for example. Insome embodiments, gate dielectric 282 and/or gate electrode 284 mayinclude a multilayer structure of two or more material layers, forexample. For instance, in one embodiment, the gate dielectric includes afirst layer of silicon dioxide on the channel region, and a second layerof hafnium oxide on the first layer. That gate electrode may include,for instance, a metal plug along with one or more workfunction layers,resistance-reducing layers, and/or barrier layers. In some embodiments,gate dielectric 282 and/or gate electrode 284 may include grading (e.g.,increasing and/or decreasing) the content/concentration of one or morematerials in at least a portion of the feature(s). Note that althoughgate dielectric 282 is only shown below gate electrode 284 in theexample embodiment of FIG. 2M, in other embodiments, the gate dielectric282 may also be present on one or both sides of gate electrode 284, suchthat the gate dielectric 282 is u-shaped (in a cross-sectional profile)may also be between gate electrode 284 and one or both of gate spacers250, for example. Numerous different gate stack configurations will beapparent in light of this disclosure.

Method 100 of FIG. 1 continues with performing 124 S/D contactprocessing to form the example resulting structure of FIG. 2P, inaccordance with some embodiments. S/D contact processing 124, in thisexample embodiment, first includes forming S/D contact trenches 290above the S/D regions 261, 262, as shown in FIG. 2P. In some suchembodiments, the contact trenches 290 may be formed using any suitabletechniques, such as performing one or more wet and/or dry etch processesto remove portions of ILD layer 270 or dopant-rich insulator cap 212 asshown, and/or any other suitable processing as will be apparent in lightof this disclosure. Such etch processing may be referred to as the S/Dcontact trench etch processing, or simply, contact trench etchprocessing. Further, in some such embodiments, the ILD may first bepatterned such that areas that are not to be removed via the contacttrench etch processing are masked off, for example. In some embodiments,one or more etch stop layers may have been formed on S/D regions 261,262 prior to performing the contact trench etch processing, to help withthe controllability of the processing (e.g., to help stop the etching tohelp prevent the etching from consuming material of the S/D regions inan undesired manner). In some such embodiments, the etch stop layer(s)may include insulator material that is dissimilar from the ILD 270material (e.g., to provide relative etch selectivity) and/or materialthat is resilient to the contact trench etch, such as a carbon-basedetch stop layer (e.g., with carbon concentration in the range of 1-80%).

Continuing from the example structure of FIG. 2P contact processing 124includes forming S/D contacts 291 above respective S/D regions 261, 262,in accordance with some embodiments. In the example structure of FIG.2P, it can be understood that S/D contacts 291 are electricallyconnected to S/D regions 261, 262, and in some cases, they may also bein physical contact with those S/D regions. In some embodiments, S/Dcontacts 291 may be formed using any suitable techniques, such asdepositing metal or metal alloy (or other suitable electricallyconductive material) in contact trenches 290. In some embodiments, S/Dcontact 291 formation may include silicidation, germanidation, and/orannealing processes, for example, where such processing may be performedto form an intervening contact layer before forming the bulk contactmetal structure, for instance. In some embodiments, S/D contacts 291 mayinclude aluminum, copper, cobalt or tungsten, although any suitableconductive metal or alloy can be used, such as silver, nickel-platinum,or nickel-aluminum, for example. Generally, in some embodiments, one ormore of the S/D contacts 291 may include a resistance reducing metal anda contact plug metal, or just a contact plug, for instance. Examplecontact resistance reducing metals include, for instance, nickel,aluminum, titanium, tantalum, nickel-platinum, or nickel aluminum,and/or other such resistance reducing and/or diffusion barrier metals oralloys. In some embodiments, S/D contacts 291 may employ lowwork-function metal material(s) and/or high work-function metalmaterial(s), depending on the particular configuration. In someembodiments, additional layers may be present in the S/D contactregions, such as adhesion layers (e.g., titanium nitride) and/or lineror barrier layers (e.g., tantalum nitride), if so desired.

FIG. 2Q illustrates another view in 3 dimensions (x,y,z) of the examplestructure of FIG. 2P, according to an embodiment. Shown in this figureare the substrate 200, and STI regions 220. Both p-MOS 261 and n-MOS 262replacement S/D material are shown after, for example, epitaxial S/Dprocessing. Dopant-rich insulator cap 212 is also shown as depositedover the pair of n-MOS S/D fins 262. Also shown in the background isgate spacer 250. Additionally, S/D isolation walls 295 are shown in thisexample embodiment.

FIG. 3A illustrates an example cross-sectional view along the plane A-Ain FIG. 2P, in accordance with some embodiments. The cross-sectionalview of FIG. 3A is provided to assist in illustrating different featuresof the structure of FIG. 2P. Therefore, the relevant description withrespect to each similarly numbered feature is equally applicable to FIG.3A. However, note that the dimensions of the features shown in FIG. 3Amay differ relative to the features in FIG. 2P, for ease ofillustration. Also note that some variations occur between thestructures, such as the shape of gate spacers 250 and the shape offinned channel region 230, for example. Further note that channel region230 shown in FIG. 3A is not native to substrate 200; however, in otherembodiments, the channel region (and thus, the material of that channelregion) may be native to substrate 200. Further still, note that theparticular S/D configuration employed in the structure of FIG. 3A is thesame S/D configuration from FIG. 2P.

In some embodiments, the length of gate electrode 284 (e.g., thedimension between spacers 250 in the Z-axis direction), which isindicated as Lg in FIG. 3A, may be any suitable length as will beapparent in light of this disclosure. For instance, in some embodiments,the gate length may be in the range of 3-100 nm (e.g., 3-10, 3-20, 3-30,3-50, 5-10, 5-20, 5-30, 5-50, 5-100, 10-20, 10-30, 10-50, 10-100, 20-30,20-50, 20-100, or 50-100 nm) or greater, for example. In someembodiments, the gate length may be less than a given threshold, such asless than 100, 50, 45, 40, 35, 30, 25, 20, 15, 10, 8, or 5 nm, or lessthan some other suitable threshold as will be apparent in light of thisdisclosure. In some embodiments, the techniques enable maintaining adesired device performance when scaling to such low thresholds, such assub-50, sub-40, sub-30, or sub-20 nm thresholds and beyond, as can beunderstood based on this disclosure. For instance, the techniques asvariously described herein can reduce short channel effects, therebyincreasing the effective channel length (dimension between the S/Dregions in the Z-axis direction). Further, the techniques describedherein may allow the gate length and the effective channel length to bethe same or approximately the same, in accordance with some embodiments.For instance, in some such embodiments, being approximately the samewith respect to the effective channel length and the gate length mayinclude that the effective channel length is within 1-10 nm (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 nm) or within 1-10% (e.g.,within 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10%) different (e.g., shorter) thanthe gate length.

FIG. 3B illustrates another example cross-sectional view, similar tothat of FIG. 3A, along the plane B-B in FIG. 2P, in accordance with someembodiments. In this view, the S/D region 262 is an n-MOS material, andthe dopant-rich insulator cap layer 212 is shown as deposited over theadjacent S/D region 262. Also, as can be seen, the dopant-rich insulatorcap layer 212 is not present adjacent to the channel region 230, due toprotection provided by the gate structure during deposition of thedopant-rich insulator cap.

Method 100 of FIG. 1 continues with completing 126 integrated circuit(IC) processing as desired, in accordance with some embodiments. Suchadditional processing to complete the IC may include back-end orback-end-of-line (BEOL) processing to form one or more metallizationlayers and/or to interconnect the transistor devices formed duringfront-end or front-end-of-line (FEOL) processing, for example. Any othersuitable processing may be performed, as will be apparent in light ofthis disclosure. Note that the processes 102-126 of method 100 are shownin a particular order for ease of description. However, one or more ofthe processes 102-126 may be performed in a different order or may notbe performed at all. For example, box 116 is an optional process thatneed not be performed in embodiments employing a gate first processflow. Recall that the techniques may be used to form a multitude ofdifferent transistor types and configurations. Although the techniquesare primarily depicted and described herein in the context of employinga dopant-rich insulator cap to reduce undesired diffusion of n-typeimpurities from source/drain structures to adjacent insulator regions ofa given n-MOS transistor having a Ge-rich channel region, the presentdisclosure is not intended to be so limited, as the techniques may beused to benefit only one side of a given channel region, and not theother, in some embodiments. Numerous variations and configurations willbe apparent in light of the present disclosure.

Example System

FIG. 4 illustrates a computing system 1000 implemented with integratedcircuit structures and/or transistor devices formed using the techniquesdisclosed herein, in accordance with some embodiments of the presentdisclosure. As can be seen, the computing system 1000 houses amotherboard 1002. The motherboard 1002 may include a number ofcomponents, including, but not limited to, a processor 1004 and at leastone communication chip 1006, each of which can be physically andelectrically coupled to the motherboard 1002, or otherwise integratedtherein. As will be appreciated, the motherboard 1002 may be, forexample, any printed circuit board, whether a main board, adaughterboard mounted on a main board, or the only board of system 1000,etc.

Depending on its applications, computing system 1000 may include one ormore other components that may or may not be physically and electricallycoupled to the motherboard 1002. These other components may include, butare not limited to, volatile memory (e.g., DRAM), non-volatile memory(e.g., ROM), a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth). Any of the components included in computingsystem 1000 may include one or more integrated circuit structures ordevices formed using the disclosed techniques in accordance with anexample embodiment. In some embodiments, multiple functions can beintegrated into one or more chips (e.g., for instance, note that thecommunication chip 1006 can be part of or otherwise integrated into theprocessor 1004).

The communication chip 1006 enables wireless communications for thetransfer of data to and from the computing system 1000. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 1006 may implementany of a number of wireless standards or protocols, including, but notlimited to, Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing system 1000 may include a plurality ofcommunication chips 1006. For instance, a first communication chip 1006may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 1006 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 1004 of the computing system 1000 includes an integratedcircuit die packaged within the processor 1004. In some embodiments, theintegrated circuit die of the processor includes onboard circuitry thatis implemented with one or more integrated circuit structures or devicesformed using the disclosed techniques, as variously described herein.The term “processor” may refer to any device or portion of a device thatprocesses, for instance, electronic data from registers and/or memory totransform that electronic data into other electronic data that may bestored in registers and/or memory.

The communication chip 1006 also may include an integrated circuit diepackaged within the communication chip 1006. In accordance with somesuch example embodiments, the integrated circuit die of thecommunication chip includes one or more integrated circuit structures ordevices formed using the disclosed techniques as variously describedherein. As will be appreciated in light of this disclosure, note thatmulti-standard wireless capability may be integrated directly into theprocessor 1004 (e.g., where functionality of any chips 1006 isintegrated into processor 1004, rather than having separatecommunication chips). Further note that processor 1004 may be a chip sethaving such wireless capability. In short, any number of processor 1004and/or communication chips 1006 can be used. Likewise, any one chip orchip set can have multiple functions integrated therein.

In various implementations, the computing system 1000 may be a laptop, anetbook, a notebook, a smartphone, a tablet, a personal digitalassistant (PDA), an ultra-mobile PC, a mobile phone, a desktop computer,a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player, adigital video recorder, or any other electronic device or system thatprocesses data or employs one or more integrated circuit structures ordevices formed using the disclosed techniques, as variously describedherein. Note that reference to a computing system is intended to includecomputing devices, apparatuses, and other structures configured forcomputing or processing information.

Further Example Embodiments

The following examples pertain to further embodiments, from whichnumerous permutations and configurations will be apparent.

Example 1 is an integrated circuit (IC) comprising: a semiconductor bodyincluding at least 75% germanium by atomic percentage; a gate structureon the semiconductor body, the gate structure including a gatedielectric and a gate electrode; a source region and a drain region bothadjacent to the gate structure such that the gate structure is betweenthe source and drain regions, at least one of the source region and thedrain region including n-type impurity; and a dopant-rich insulator capregion between the at least one of the source region and the drainregion and an undoped insulator region, the dopant-rich insulator capregion including the n-type impurity, the dopant-rich insulator capregion distinct from the undoped insulator region.

Example 2 includes the subject matter of Example 1, wherein the n-typeimpurity is phosphorous.

Example 3 includes the subject matter of Examples 1 or 2, wherein theconcentration of the n-type impurity in the dopant-rich insulator capregion is in the range of 1 to 10 atomic %.

Example 4 includes the subject matter of any of Examples 1-3, whereinthe thickness of the dopant-rich insulator cap region is in the range of10 nanometers to 100 nanometers, the thickness being the distancebetween a first adjacent undoped insulator on a first side of the atleast one of the source region and the drain region, and a secondadjacent undoped insulator on a second side of the at least one of thesource region and the drain region.

Example 5 includes the subject matter of any of Examples 1-4, whereinthe height of the dopant-rich insulator cap region is in the range of 10nanometers to 200 nanometers, the height being a distance extendingperpendicularly from a surface of a shallow trench isolation (STI)region adjacent the at least one of the source region and the drainregion.

Example 6 includes the subject matter of any of Examples 1-5, whereinthe dopant-rich insulator cap region includes silicon dioxide.

Example 7 includes the subject matter of any of Examples 1-6, whereinthe semiconductor body further includes at least one of silicon, indium,gallium, arsenic, antimony, and nitrogen.

Example 8 includes the subject matter of any of Examples 1-7, whereinthe germanium concentration of the semiconductor body is 98 atomicpercent or more.

Example 9 includes the subject matter of any of Examples 1-8, whereinthe semiconductor body further includes up to 2% tin by atomicpercentage.

Example 10 includes the subject matter of any of Examples 1-9, whereinin addition to the n-type impurity, the source region and drain regionare compositionally distinct from the semiconductor body, the sourceregion and drain region including at least one of silicon and germanium.

Example 11 includes the subject matter of any of Examples 1-10, whereinin addition to the n-type impurity, the source region and drain regionare compositionally different from the semiconductor body, the sourceregion and drain region further including at least one of silicon,indium, gallium, arsenic, antimony, and nitrogen.

Example 12 includes the subject matter of any of Examples 1-11, whereinthe source region and drain region further include up to 2% tin byatomic percentage.

Example 13 includes the subject matter of any of Examples 1-12, whereinthe n-type impurity is arsenic.

Example 14 includes the subject matter of any of Examples 1-13, whereinthe semiconductor body is on a fin stub, and the dopant-rich insulatorcap region is on opposing sidewalls of the fin stub as well as opposingsidewalls of the semiconductor body.

Example 15 includes the subject matter of any of Examples 1-14, whereinthe at least one of the source region and the drain region is on the finstub, and the dopant-rich insulator cap region is on opposing sidewallsof the fin stub as well as opposing sidewalls of the at least one of thesource region and the drain region.

Example 16 includes the subject matter of any of Examples 1-15, whereinthe fin stub is part of an underlying semiconductor substrate.

Example 17 includes the subject matter of any of Examples 1-16, whereinthe substrate is silicon and the semiconductor body includes at leastone of germanium, gallium, arsenic, indium, antimony, and nitrogen.

Example 18 includes the subject matter of any of Examples 1-17, furthercomprising a first contact structure in the dopant-rich insulator capregion and on the source region, and a second contact structure in thedopant-rich insulator cap region and on the drain region.

Example 19 includes the subject matter of any of Examples 1-18, whereinthe dopant-rich insulator cap region is on the uppermost surface of theat least one of the source region and the drain region.

Example 20 includes the subject matter of any of Examples 1-19, whereinthe semiconductor body is a fin.

Example 21 includes the subject matter of any of Examples 1-20, whereinthe semiconductor body includes one or more nanowires.

Example 22 includes the subject matter of any of Examples 1-21, whereinthe semiconductor body includes one or more nanoribbons.

Example 23 includes the subject matter of any of Examples 1-22, whereinthe gate structure further includes a first gate spacer between thesource region and the gate electrode, and a second gate spacer betweenthe drain region and the gate electrode.

Example 24 is a computing system comprising the IC of any of claims1-23.

Example 25 is a method of forming an integrated circuit (IC), the methodcomprising: forming a semiconductor body including at least 75%germanium by atomic percentage; forming a gate structure on thesemiconductor body, the gate structure including a gate dielectric and agate electrode; forming a source region and a drain region both adjacentto the gate structure such that the gate structure is between the sourceand drain regions, at least one of the source region and the drainregion including n-type impurity; and forming a dopant-rich insulatorcap region between the at least one of the source region and the drainregion and an undoped insulator region, the dopant-rich insulator capregion including the n-type impurity, the dopant-rich insulator capregion distinct from the undoped insulator region.

Example 26 includes the subject matter of Example 25, wherein the n-typeimpurity is phosphorous.

Example 27 includes the subject matter of Examples 25 or 26, wherein theconcentration of the n-type impurity in the dopant-rich insulator capregion is in the range of 1 to 10 atomic %.

Example 28 includes the subject matter of any of Examples 25-27, whereinthe thickness of the dopant-rich insulator cap region is in the range of10 nanometers to 100 nanometers, the thickness being the distancebetween a first adjacent undoped insulator on a first side of the atleast one of the source region and the drain region, and a secondadjacent undoped insulator on a second side of the at least one of thesource region and the drain region.

Example 29 includes the subject matter of any of Examples 25-28, whereinthe height of the dopant-rich insulator cap region is in the range of 10nanometers to 200 nanometers, the height being a distance extendingperpendicularly from a surface of a shallow trench isolation (STI)region adjacent the at least one of the source region and the drainregion.

Example 30 includes the subject matter of any of Examples 25-29, whereinthe germanium concentration of the semiconductor body is 98 atomicpercent or more.

Example 31 includes the subject matter of any of Examples 25-30, whereinthe dopant-rich insulator cap region includes silicon dioxide.

Example 32 includes the subject matter of any of Examples 25-31, whereinthe semiconductor body further includes at least one of silicon, indium,gallium, arsenic, antimony, and nitrogen.

Example 33 includes the subject matter of any of Examples 25-32, whereinthe semiconductor body further includes up to 2% tin by atomicpercentage.

Example 34 includes the subject matter of any of Examples 25-33, whereinin addition to the n-type impurity, the source region and drain regionare compositionally distinct from the semiconductor body, the sourceregion and drain region including at least one of silicon and germanium.

Example 35 includes the subject matter of any of Examples 25-34, whereinin addition to the n-type impurity, the source region and drain regionare compositionally different from the semiconductor body, the sourceregion and drain region further including at least one of silicon,indium, gallium, arsenic, antimony, and nitrogen.

Example 36 includes the subject matter of any of Examples 25-35, whereinthe source region and drain region further include up to 2% tin byatomic percentage.

Example 37 includes the subject matter of any of Examples 25-36, whereinthe n-type impurity is arsenic.

Example 38 includes the subject matter of any of Examples 25-37, whereinthe semiconductor body is on a fin stub, and the dopant-rich insulatorcap region is on opposing sidewalls of the fin stub as well as opposingsidewalls of the semiconductor body.

Example 39 includes the subject matter of any of Examples 25-38, whereinthe at least one of the source region and the drain region is on the finstub, and the dopant-rich insulator cap region is on opposing sidewallsof the fin stub as well as opposing sidewalls of the at least one of thesource region and the drain region.

Example 40 includes the subject matter of any of Examples 25-39, whereinthe fin stub is part of an underlying semiconductor substrate.

Example 41 includes the subject matter of any of Examples 25-40, whereinthe substrate is silicon and the semiconductor body includes at leastone of germanium, gallium, arsenic, indium, antimony, and nitrogen.

Example 42 includes the subject matter of any of Examples 25-41, furthercomprising forming a first contact structure in the dopant-richinsulator cap region and on the source region, and a second contactstructure in the dopant-rich insulator cap region and on the drainregion.

Example 43 includes the subject matter of any of Examples 25-42, whereinthe dopant-rich insulator cap region is on the uppermost surface of theat least one of the source region and the drain region.

Example 44 includes the subject matter of any of Examples 25-43, whereinthe semiconductor body is a fin.

Example 45 includes the subject matter of any of Examples 25-44, whereinthe semiconductor body includes one or more nanowires.

Example 46 includes the subject matter of any of Examples 25-45, whereinthe semiconductor body includes one or more nanoribbons.

Example 47 includes the subject matter of any of Examples 25-46, whereinthe gate structure further includes a first gate spacer between thesource region and the gate electrode, and a second gate spacer betweenthe drain region and the gate electrode.

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention,in the use of such terms and expressions, of excluding any equivalentsof the features shown and described (or portions thereof), and it isrecognized that various modifications are possible within the scope ofthe claims. Accordingly, the claims are intended to cover all suchequivalents. Various features, aspects, and embodiments have beendescribed herein. The features, aspects, and embodiments are susceptibleto combination with one another as well as to variation andmodification, as will be appreciated in light of this disclosure. Thepresent disclosure should, therefore, be considered to encompass suchcombinations, variations, and modifications. It is intended that thescope of the present disclosure be limited not be this detaileddescription, but rather by the claims appended hereto. Future filedapplications claiming priority to this application may claim thedisclosed subject matter in a different manner, and may generallyinclude any set of one or more elements as variously disclosed orotherwise demonstrated herein.

1-25. (canceled)
 26. An integrated circuit (IC) comprising: a body ofsemiconductor material including at least 75% germanium by atomicpercentage; a gate structure on the body, the gate structure including agate dielectric and a gate electrode; a source region and a drain regionboth adjacent to the gate structure such that the gate structure isbetween the source and drain regions, at least one of the source regionand the drain region including n-type impurity; and a dopant-richinsulator cap region between the at least one of the source region andthe drain region and an undoped insulator region, the dopant-richinsulator cap region including the n-type impurity, the dopant-richinsulator cap region distinct from the undoped insulator region.
 27. TheIC of claim 26, wherein the n-type impurity is phosphorous.
 28. The ICof claim 26, wherein the n-type impurity is arsenic.
 29. The IC of claim26, wherein the body further includes at least one of silicon, indium,gallium, arsenic, antimony, and nitrogen.
 30. The IC of claim 26,wherein the germanium concentration of the body is 98 atomic percent ormore.
 31. The IC of claim 26, wherein the body further includes up to 2%tin by atomic percentage.
 32. The IC of claim 26, wherein theconcentration of the n-type impurity in the dopant-rich insulator capregion is in the range of 1 to 10 atomic %.
 33. The IC of claim 26,wherein the thickness of the dopant-rich insulator cap region is in therange of 10 nanometers to 100 nanometers, the thickness being thedistance between a first adjacent undoped insulator on a first side ofthe at least one of the source region and the drain region, and a secondadjacent undoped insulator on a second side of the at least one of thesource region and the drain region, and wherein the height of thedopant-rich insulator cap region is in the range of 10 nanometers to 200nanometers, the height being a distance extending perpendicularly from asurface of a shallow trench isolation (STI) region adjacent the at leastone of the source region and the drain region.
 34. The IC of claim 26,wherein the dopant-rich insulator cap region includes silicon dioxide.35. The IC of claim 26, wherein in addition to the n-type impurity, thesource region and drain region are compositionally distinct from thebody, the source region and drain region including at least one ofsilicon and germanium, and the source region and drain region arecompositionally different from the body, the source region and drainregion further including at least one of silicon, indium, gallium,arsenic, antimony, and nitrogen.
 36. The IC of claim 26, wherein thesource region and drain region further include up to 2% tin by atomicpercentage.
 37. The IC of claim 26, wherein the body is on a fin stub,and the dopant-rich insulator cap region is on opposing sidewalls of thefin stub as well as opposing sidewalls of the body, and wherein the atleast one of the source region and the drain region is on the fin stub,and the dopant-rich insulator cap region is on opposing sidewalls of thefin stub as well as opposing sidewalls of the at least one of the sourceregion and the drain region.
 38. The IC of claim 37, wherein the finstub is part of an underlying substrate of semiconductor material. 39.The IC of claim 38, wherein the substrate is silicon and the bodyincludes at least one of germanium, gallium, arsenic, indium, antimony,and nitrogen.
 40. The IC of claim 26, further comprising a first contactstructure in the dopant-rich insulator cap region and on the sourceregion, and a second contact structure in the dopant-rich insulator capregion and on the drain region.
 41. An integrated circuit (IC)comprising: a fin or nanowire including at least 75% germanium by atomicpercentage; a fin stub below the fin or nanowire; a gate structure onthe fin or nanowire, the gate structure including a gate dielectric anda gate electrode; a source region and a drain region both adjacent tothe gate structure such that the gate structure is between the sourceand drain regions, at least one of the source region and the drainregion including n-type impurity; and a dopant-rich insulator cap regionbetween the at least one of the source region and the drain region andan undoped insulator region, the dopant-rich insulator cap regionincluding the n-type impurity, the dopant-rich insulator cap regiondistinct from the undoped insulator region, wherein the dopant-richinsulator cap region is on an uppermost surface of the at least one ofthe source region and the drain region, and the dopant-rich insulatorcap region is on opposing sidewalls of the fin stub.
 42. The IC of claim41, wherein the at least one of the source region and the drain regionis on the fin stub, and the dopant-rich insulator cap region is onopposing sidewalls of the fin stub as well as opposing sidewalls of theat least one of the source region and the drain region.
 43. Anintegrated circuit (IC) comprising: a body of semiconductor materialincluding at least 75% germanium by atomic percentage; a gate structureon the body, the gate structure including a gate dielectric and a gateelectrode; a source region and a drain region both adjacent to the gatestructure such that the gate structure is between the source and drainregions, at least one of the source region and the drain regionincluding n-type impurity; and a dopant-rich insulator cap regionbetween the at least one of the source region and the drain region andan undoped insulator region, the dopant-rich insulator cap regionincluding the n-type impurity, the dopant-rich insulator cap regiondistinct from the undoped insulator region, wherein the dopant-richinsulator cap region is on an uppermost surface of the at least one ofthe source region and the drain region.
 44. The IC of claim 43, whereinthe thickness of the dopant-rich insulator cap region is in the range of10 nanometers to 100 nanometers, the thickness being the distancebetween a first adjacent undoped insulator on a first side of the atleast one of the source region and the drain region, and a secondadjacent undoped insulator on a second side of the at least one of thesource region and the drain region
 45. The IC of claim 43, wherein thegate structure further includes a first gate spacer between the sourceregion and the gate electrode, and a second gate spacer between thedrain region and the gate electrode.